194 research outputs found
Total Variation Regularized Tensor RPCA for Background Subtraction from Compressive Measurements
Background subtraction has been a fundamental and widely studied task in
video analysis, with a wide range of applications in video surveillance,
teleconferencing and 3D modeling. Recently, motivated by compressive imaging,
background subtraction from compressive measurements (BSCM) is becoming an
active research task in video surveillance. In this paper, we propose a novel
tensor-based robust PCA (TenRPCA) approach for BSCM by decomposing video frames
into backgrounds with spatial-temporal correlations and foregrounds with
spatio-temporal continuity in a tensor framework. In this approach, we use 3D
total variation (TV) to enhance the spatio-temporal continuity of foregrounds,
and Tucker decomposition to model the spatio-temporal correlations of video
background. Based on this idea, we design a basic tensor RPCA model over the
video frames, dubbed as the holistic TenRPCA model (H-TenRPCA). To characterize
the correlations among the groups of similar 3D patches of video background, we
further design a patch-group-based tensor RPCA model (PG-TenRPCA) by joint
tensor Tucker decompositions of 3D patch groups for modeling the video
background. Efficient algorithms using alternating direction method of
multipliers (ADMM) are developed to solve the proposed models. Extensive
experiments on simulated and real-world videos demonstrate the superiority of
the proposed approaches over the existing state-of-the-art approaches.Comment: To appear in IEEE TI
The Invariant Unscented Kalman Filter
International audienceThis article proposes a novel approach for nonlinear state estimation. It combines both invariant observers theory and unscented filtering principles whitout requiring any compatibility condition such as proposed in the -IUKF algorithm. The resulting algorithm, named IUKF (Invariant Unscented Kalman Filter), relies on a geometrical-based constructive method for designing filters dedicated to nonlinear state estimation problems while preserving the physical invariances and systems symmetries. Within an invariant framework, this algorithm suggests a systematic approach to determine all the symmetry- preserving terms without requiring any linearization and highlighting remarkable invariant properties. As a result, the estimated covariance matrices of the IUKF converge to quasi-constant values due to the symmetry-preserving property provided by the invariant framework. This result enables the development of less conservative robust control strategies. The designed IUKF method has been successfully applied to some relevant practical problems such as the estimation of attitude for aerial vehicles using low-cost sensors reference systems. Typical experimental results using a Parrot quadrotor are provided in this pape
Spatially resolved CO SLED of the Luminous Merger Remnant NGC 1614 with ALMA
We present high-resolution (1".0) Atacama Large Millimeter/submillimeter
Array (ALMA) observations of CO (1-0) and CO (2- 1) rotational transitions
toward the nearby IR-luminous merger NGC 1614 supplemented with ALMA archival
data of CO (3-2), and CO (6-5) transitions. The CO (6-5) emission arises from
the starburst ring (central 590 pc in radius), while the lower- CO lines are
distributed over the outer disk ( 3.3 kpc in radius). Radiative transfer
and photon dominated region (PDR) modeling reveal that the starburst ring has a
single warmer gas component with more intense far-ultraviolet radiation field
( 10 cm, 42 K, and
10) relative to the outer disk (
10 cm, 22 K, and
10). A two-phase molecular interstellar medium with a warm and
cold ( 70 K and 19 K) component is also an applicable model for the
starburst ring. A possible source for heating the warm gas component is
mechanical heating due to stellar feedback rather than PDR. Furthermore, we
find evidence for non-circular motions along the north-south optical bar in the
lower- CO images, suggesting a cold gas inflow. We suggest that star
formation in the starburst ring is sustained by the bar-driven cold gas inflow,
and starburst activities radiatively and mechanically power the CO excitation.
The absence of a bright active galactic nucleus can be explained by a scenario
that cold gas accumulating on the starburst ring is exhausted as the fuel for
star formation, or is launched as an outflow before being able to feed to the
nucleus.Comment: 20 pages, 19 figures, 2 tables, accepted for publication in Ap
HiDAnet: RGB-D Salient Object Detection via Hierarchical Depth Awareness
RGB-D saliency detection aims to fuse multi-modal cues to accurately localize
salient regions. Existing works often adopt attention modules for feature
modeling, with few methods explicitly leveraging fine-grained details to merge
with semantic cues. Thus, despite the auxiliary depth information, it is still
challenging for existing models to distinguish objects with similar appearances
but at distinct camera distances. In this paper, from a new perspective, we
propose a novel Hierarchical Depth Awareness network (HiDAnet) for RGB-D
saliency detection. Our motivation comes from the observation that the
multi-granularity properties of geometric priors correlate well with the neural
network hierarchies. To realize multi-modal and multi-level fusion, we first
use a granularity-based attention scheme to strengthen the discriminatory power
of RGB and depth features separately. Then we introduce a unified cross
dual-attention module for multi-modal and multi-level fusion in a
coarse-to-fine manner. The encoded multi-modal features are gradually
aggregated into a shared decoder. Further, we exploit a multi-scale loss to
take full advantage of the hierarchical information. Extensive experiments on
challenging benchmark datasets demonstrate that our HiDAnet performs favorably
over the state-of-the-art methods by large margins
Unsupervised Learning of Category-Specific Symmetric 3D Keypoints from Point Sets
Automatic discovery of category-specific 3D keypoints from a collection of objects of a category is a challenging problem. The difficulty is added when objects are represented by 3D point clouds, with variations in shape and semantic parts and unknown coordinate frames. We define keypoints to be category-specific, if they meaningfully represent objects’ shape and their correspondences can be simply established order-wise across all objects. This paper aims at learning such 3D keypoints, in an unsupervised manner, using a collection of misaligned 3D point clouds of objects from an unknown category. In order to do so, we model shapes defined by the keypoints, within a category, using the symmetric linear basis shapes without assuming the plane of symmetry to be known. The usage of symmetry prior leads us to learn stable keypoints suitable for higher misalignments. To the best of our knowledge, this is the first work on learning such keypoints directly from 3D point clouds for a general category. Using objects from four benchmark datasets, we demonstrate the quality of our learned keypoints by quantitative and qualitative evaluations. Our experiments also show that the keypoints discovered by our method are geometrically and semantically consistent
The Planetary Mass Companion 2MASS1207-3932 B: Temperature, Mass and Evidence for an Edge-On Disk
We present J-band imaging and H+K-band low-resolution spectroscopy of
2MASS1207-3932 AB, obtained with VLT NACO. For the putative planetary mass
secondary, we find J = 20.0+/-0.2 mag. The HK spectra of both components imply
low gravity, and a dusty atmosphere for the secondary. Comparisons to synthetic
spectra yield Teff_A ~ 2550+/-150K, and Teff_B ~ 1600+/-100K, consistent with
their late-M and mid-to-late L types. For these Teff, and an age of 5-10 Myrs,
evolutionary models imply M_A ~ 24+/-6 M_Jup and M_B ~ 8+/-2 M_Jup. Independent
comparisons of these models to the observed colors, spanning ~I to L', also
yield the same masses and temperatures. Our primary mass agrees with other
recent analyses; however, our secondary mass, while still in the planetary
regime, is 2-3 times larger than claimed previously. This discrepancy can be
traced to the luminosities: while the absolute photometry and Mbol of the
primary agree with theoretical predictions, the secondary is ~ 2.5+/-0.5 mag
fainter than expected in all bands from I to L' and in Mbol. This accounts for
the much lower secondary mass (and temperature) derived earlier. We argue that
this effect is highly unlikely to result from a variety of model-related
problems, and is instead real. This conclusion is bolstered by the absence of
any luminosity problems in either the primary, or in AB Pic B which we also
analyse. We therefore suggest grey extinction in 2M1207B, due to occlusion by
an edge-on circum-secondary disk. This is consistent with the observed
properties of edge-on disks around T Tauri stars, and with the known presence
of a high-inclination evolved disk around the primary. Finally, the system's
implied mass ratio of ~0.3 suggests a binary-like formation scenario.
(abridged)Comment: Accepted by The Astrophysical Journal, 43 pages text + 16 figs + 1
tabl
A convolutional neural network based Chinese text detection algorithm via text structure modeling
Text detection in natural scene environment plays an important role in many computer vision applications. While existing text detection methods are focused on English characters, there is strong application demands on text detection in other languages, such as Chinese. As Chinese characters are much more complex than English characters, innovative and more efficient text detection techniques are required for Chinese texts. In this paper, we present a novel text detection algorithm for Chinese characters based on a specific designed convolutional neural network (CNN). The CNN model contains a text structure component detector layer, a spatial pyramid layer and a multi-input-layer deep belief network (DBN). The CNN is pretrained via a convolutional sparse auto-encoder (CSAE) in an unsupervised way, which is specifically designed for extracting complex features from Chinese characters. In particular, the text structure component detectors enhance the accuracy and uniqueness of feature descriptors by extracting multiple text structure components in various ways. The spatial pyramid layer is then introduced to enhance the scale invariability of the CNN model for detecting texts in multiple scales. Finally, the multi-input-layer DBN is used as the fully connected layers in the CNN model to ensure that features from multiple scales are comparable. A multilingual text detection dataset, in which texts in Chinese, English and digits are labeled separately, is set up to evaluate the proposed text detection algorithm. The proposed algorithm shows a significant 10% performance improvement over the baseline CNN algorithms. In addition the proposed algorithm is evaluated over a public multilingual image benchmark and achieves state-of-the-art results for text detection under multiple languages. Furthermore a simplified version of the proposed algorithm with only general components is compared to existing general text detection algorithms on the ICDAR 2011 and 2013 datasets, showing comparable detection performance to the existing algorithms
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